You create a custom field type and a corresponding custom field control. You need to ensure that the field type is available to users when they create list columns.

What should you do?

A.
Include the AtRegister directive on the Master Page

B.
Add a Safe Control element to the web.config file

C.
Add the custom field control markup to the fldNew.aspx page

D.
Create a field type definition file in the 12.Template.XML folder